Subnet / CIDR Calculator
Enter an IPv4 address with a prefix or netmask to see the subnet.
Subnets, in plain English
An IP address is a bit like a street address: part of it says which neighbourhood you’re in, and part says which house. A subnet is that neighbourhood — a block of addresses that belong together.
The /22 in 10.0.0.0/22 is just shorthand for how big the block is: “the first 22 bits are the neighbourhood, the rest are house numbers.” The smaller the number after the slash, the bigger the block:
/24→ 256 addresses (one small street)/22→ 1,024 addresses (a few streets)/16→ 65,536 addresses (a whole district)
Two addresses sit on the same subnet when they share those neighbourhood bits — which is exactly what the netmask works out. The network address is the first slot on the block, the broadcast address is the special “everyone here” slot at the very end, and everything in between is a usable host you can hand out to a real device.
Why bother? Subnetting is how a big network gets carved into tidy, secure pieces — servers kept apart from laptops, one tenant apart from another — and how routers decide whether a packet stays local or heads out to the wider internet.
Paste any address above and the tool does the bit-twiddling for you: the range, the mask, how many hosts fit, and whether it’s a private or public block.